The effects of general anaesthesia on antroduodenal motility, gastric pH and gastric emptying in man

Abstract

This survey was based on five recently published papers. The aims of the studies were to to investigate the effect of general anaesthesia on antroduodenal motility, gastric pH and gastric emptying. Antroduodenal motility was measured by manometry, gastric pH by a stomach microelectrode and gastric emptying rate using paracetamol absorption as an index. Two studies deal with antroduodenal motility during basal conditions and after administration of paracetamol and diazepam in 11 healthy volunteers. Three studies deal with the effects of 4 different methods of general anaesthesia on antroduodenal motility, gastric pH and gastric emptying rate in 43 patients undergoing orthopedic or plastic surgery not involving the abdomen having four different methods of general anaesthesia. In the healthy volunteers a close connection between antral activity and gastric emptying rate was found. Paracetamol had no effects on gastric pH. The changes in motility (a shortening of phase III and a decline in the incidence of antral phase III activity) were minor and ascribed to diurnal variations and by a possible stimulation of antral activity by the positioning of the manometric tube. It was found that no paracetamol was absorbed in the quiescent phase I, irrespective of its duration, and that the absorption rate of paracetamol correlated with the duration of phase II and the occurrence of antral activity during phases II and III. The effects of premedication with diazepam on antroduodenal motility, gastric pH and gastric emptying rate was investigated in the same healthy volunteers prior to the patient studies. Also in this study a correlation between antral activity and gastric emptying rate was found. Furthermore, it was observed that some volunteers had fast gastric emptying rate, indicated by fast absorption of paracetamol, the first study day and slow the second. It seemed that any intra- or interindividual variation in gastric emptying rate arises from individual variations in antroduodenal motility. Diazepam tended to increase gastric emptying rate by enhancing the amplitudes of antral contractions and the motility index during phase II and pH of the gastric juice increased. Gastroduodenal motility was found to be normal in patients awaiting elective orthopedic or plastic surgery when premedicated with diazepam. pH of the gastric contents was not different from the findings in volunteers after administration of diazepam. All methods of general anaesthesia reduced the duration of the interdigestive motility complex, mainly by a reduction of phase II. General anaesthesia with halothane and enflurane depressed antral motility.(ABSTRACT TRUNCATED AT 400 WORDS)